code: def test_sprites_gray(self):
      # Get MNIST
      (x, _), (_, _), _, _ = load_mnist(raw=True)
      n = 100
      x = x[:n]
  
      sprite = create_sprite(x)
      f_name = "test_sprite_mnist.png"
      path = os.path.join(config.ART_DATA_PATH, f_name)
      save_image(sprite, path)
      self.assertTrue(os.path.isfile(path))
  
      os.remove(path)
  
file_path: adversarial-robustness-toolbox/tests/test_visualization.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  import os.path
  import unittest
  import numpy
  from art import config
  from art.utils import load_mnist, load_cifar10
  from art.visualization import create_sprite, convert_to_rgb, save_image, plot_3d
  from tests.utils import master_seed
label_desc: Use image node_id 4 for calling the TestVisualization obj's underlying member method code with example usage: obj.test_sprites_gray() without return types